This invention relates to power inductors in general and more particularly to an improved inductor having multiple windings for use in power circuits.
There are a great many circuits which employ multiple winding inductors for the conversion, control and conditioning of electric power. Essentially, such inductors are employed in the field of power electronics. In this field the primary characteristics of electric power which are subject to control includes its basic form (AC or DC), its effective voltage or current, its frequency and power factor. The control of electric power is frequently desired as a means for achieving control or regulation of one or more nonelectrical parameters as for example the speed of a motor, the temperature of an oven, the intensity of lighting as well as the conversion of power from one form to another such as from AC to DC or from DC to AC.
In order to perform such control, there are hosts of known circuits which have been generally utilized in the field of power electronics. Such circuits are designated as power conditioners, converters, inverters, power supplies and motor controls. Essentially, these particular circuits as well as many others operate to control or distribute power in a specified environment and for a particular purpose.
As such, all of the above circuits employ inductors to implement the efficient transfer of such power. The main factor is designing any inductor for use in such circuits is to provide a device that has a minimum leakage inductance between the multiwindings. One must understand that while an inductor and a transformer appear to be similar devices, they are, in fact, quite different. A transformer is intended to couple energy and energy storage is undesirable, while an inductor is primarily intended to store energy. This difference is important as many of the above noted circuits employ both transformers and inductors.
The prior art was concerned with providing an efficient multiwinding inductor which could operate efficiently and reliably in the type of circuits as indicated above. In fact, the prior art is replete with many articles and patents which attempt to show the design and construction of multiwinding inductors for different circuit applications. See for example an article entitled "Designing Optimal Multi-Output Converters with a Coupled Inductor Current-Driven Topology" by L. H. Dixon, Jr., and C. J. Baranowski, a paper presented at the Powercon Eight Convention in Dallas, Tex. in April, 1981. This paper examines the relative merits of several topology approaches to the design of multiple-output switching power converters. The paper describes a design approach using a coupled inductor current-driven (CICD) buck regulator topology, with emphasis on the optimal design of the coupled inductor in order to minimize its leakage reactance. The paper is available through the Unitrode Corporation of Lexington, MA. This paper, as well as many other articles, attempts to define the construction and implementation of an inductor for use in the field of power electronics.
In any event, the prior art attempts to generally improve circuit operation and improve the efficiency of the inductor have failed to solve the many problems attendant with such circuits. It is, therefore, an object of the present invention to provide a unique form of inductor and associated circuitry in which the inductor is incorporated.
It is another object of this invention to provide an improved inductor and circuitry which exhibits an increased overall efficiency together with a substantial reduction of the magnitude of filter capacitors necessary in the circuit.
It is still a further object of the present invention to provide a multiwinding inductor or choke exhibiting unique properties in order to enable the same to operate in a multiplicity of power control circuits, as for example multi-output power supplies, inverters and so on.